In my experiance, 6+ cars with airdams, I have gained 5%-15%. Worst is my b4000 1mpg for a 19mpg truck, best was my previous Lincoln Town Car, 3+ mpg on a 23 mpg car.
My Celica is avg with about 8%, 2mpg with a 26 mpg car. it is going to get a front belly/splitter and a better designed airdam.
Let me know if you have any questions about airdams.
http://ecomodder.com/forum/showthrea...gts-21369.html